<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .container {
            width: 100vw;
            height: 400px;
            outline: 10px solid red;
            /* 进入托管模式 */
            display: flex;
            /* 调整主轴对齐 */
            justify-content: space-evenly;
            /* 侧轴居中 */
            align-items: center;
        }
        .container .item {
            /* width: 100px; */
            height: 100px;
            outline: 10px solid red;
            line-height: 100px;
            text-align: center;
            font-size: 50px;
        }
        .container .item:nth-child(1) {
            width: 200px;
        }
        .container .item:nth-child(2) {
            flex: 1;
        }
    </style>
</head>
<body>
    <div class="container">
        <div class="item">1</div>
        <div class="item">2</div>
    </div>
</body>
</html>